1. Field of the Invention
The present invention relates to lubricating oil dispersants and dispersant viscosity index improvers prepared from N-allyl amide graft copolymers. More particularly, this invention relates to dispersants and dispersant viscosity index improvers comprising star-shaped polymers having an N-allyl amide grafted thereonto.
2. Related Art
U.S. Pat. No. 4,519,929 discloses N-allyl amide graft copolymers wherein an N-allyl amide is grafted onto an olefin polymer backbone. Such copolymers are useful as ashless dispersants and, in the case of high molecular weight materials, as viscosity index improvers. U.S. Pat. No. 4,146,489 discloses graft copolymers wherein a vinyl-substituted nitrogen compound, such as vinyl pyridine or N-vinyl pyrrolidone, is grafted onto an olefin backbone. U.S. Pat. No. 4,160,739 discloses graft copolymers wherein maleic anhydride and a comonomer, such as methyl methacrylate, are grafted onto an olefin backbone and subsequently amidated.
U.S. Pat. No. 4,116,917 discloses hydrogenated star-shaped polymers useful as viscosity index improvers, such polymers possessing thickening efficiency at high temperature while also possessing low temperature viscosity characteristics, oxidative and permanent shear stability and improved temporary shear loss.
U.S. Pat. Nos. 4,141,847; 4,427,834; 4,490,267: and 4,557,849 disclose functionalized star-shaped polymers having dispersant and/or viscosity index improving properties.